US6166533A - Frequency spectrum analyzer with high C/N ratio - Google Patents
Frequency spectrum analyzer with high C/N ratio Download PDFInfo
- Publication number
- US6166533A US6166533A US09/170,301 US17030198A US6166533A US 6166533 A US6166533 A US 6166533A US 17030198 A US17030198 A US 17030198A US 6166533 A US6166533 A US 6166533A
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- frequency
- signal
- local
- local signal
- oscillator
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
- G01R23/16—Spectrum analysis; Fourier analysis
- G01R23/173—Wobbulating devices similar to swept panoramic receivers
Definitions
- This invention relates to a frequency spectrum analyzer for analyzing frequency spectrum of an input signal, and more particularly, to a frequency spectrum analyzer having a high carrier wave to noise (C/N) ratio for analyzing frequency spectrum of an input signal with a wide dynamic range, high resolution, and low noise.
- C/N carrier wave to noise
- Frequency spectrum analyzers are widely used for analyzing frequency spectrum of an incoming signal in a frequency domain. Typically in such a frequency spectrum analyzer, levels of frequency spectrum are displayed in a vertical direction with respect to a frequency range in a horizontal direction.
- a frequency spectrum analyzer includes three or more frequency converters connected in series each of which is formed of a frequency mixer, a local oscillator and a band pass filter to produce intermediate frequency (IF) signals without image (spurious) responses.
- the frequency spectrum analyzer of FIG. 3 includes three frequency converters.
- the first frequency converter is formed of a first frequency mixer 11, a first IF filter 21 and a first local oscillator 31.
- the second frequency converter is formed of a second frequency mixer 12, a second IF filter 22 and a second local oscillator 32.
- the third frequency converter is formed of a third frequency mixer 13, a third IF filter 23 and a third local oscillator 33.
- the frequency spectrum analyzer further includes a ramp wave generator 50, a detector 60 and a display 70.
- the first local oscillator 31 is a sweep frequency oscillator whose frequency is linearly swept by a ramp wave from the ramp wave generator 50.
- the second and third local oscillators are fixed frequency oscillators. The frequency of the first local signal is higher than that of the second and third local signals.
- An input signal F1 to be analyzed is mixed with the first local signal by the first frequency mixer 11, thereby producing first IF signals having both sum and difference frequencies between the input and first local signals.
- the first IF signal is provided to the second frequency mixer 12 where it is mixed with the second local signal from the second local oscillator 32.
- the second frequency mixer produces second IF signals having both sum and difference frequencies between the first IF signal and the second local signal.
- the second IF signal is provided to the third frequency mixer 13 where it is mixed with the third local signal from the third local oscillator 33.
- the third frequency mixer produces third IF signals having both sum and difference frequencies between the second IF signal and the third local signal.
- the third IF signal from the third IF filter 23 is provided to the detector 60 where a DC voltage proportional to the AC power level of the third IF signal is produced.
- the DC voltage is provided to the display 70 where it is displayed in a vertical axis as a power level. Since the ramp wave is also applied to the display 70 for driving a horizontal axis thereof, the display screen shows frequency spectrum of the input signal F1 in a frequency domain. In such a frequency domain analysis, the power level is shown in the vertical direction while the frequency range (span) is shown in the horizontal direction.
- a frequency spectrum analyzer employs such multiple stages of frequency converters for eliminating image frequencies (spurious responses) by selecting appropriate frequencies in the local signals and IF signals. Further to eliminating the spurious responses, it is also important for a frequency spectrum analyzer to have a high carrier wave to noise (C/N) ratio to analyze an input signal with high sensitivity and resolution.
- C/N carrier wave to noise
- a C/N ratio of a spectrum analyzer is determined by C/N ratios (purity) of local signals used therein. This is because phase noise of local oscillators is usually larger than noise floors of other components in the spectrum analyzer. It is also known in the art that a C/N ratio of a fixed frequency oscillator is higher than that of a sweep frequency oscillator. Further, an oscillator having a highly selective resonant circuit such as a crystal oscillator has a higher C/N ratio than other types of oscillators.
- the first local oscillator 31 is a wide range sweep oscillator typically using a YIG (yttrium-iron-garnet) resonator.
- the second and third local oscillators 32 and 33 are fixed frequency oscillators.
- a crystal oscillator with high stability is usually used as the third local oscillator 33.
- degrees of phase noise in the first to third local oscillators will be expressed in the following order:
- ⁇ LO1 denotes the phase noise of the first local oscillator 31
- ⁇ LO2 denotes the phase noise of the second local oscillator 32
- ⁇ LO3 denotes the phase noise of the third local oscillator 33.
- phase noise ⁇ N of the frequency spectrum analyzer When the noise floor of other components in the spectrum analyzer is lower than the phase noise of local oscillators, and the phase noise of the local oscillators is random noise, overall phase noise ⁇ N of the frequency spectrum analyzer will be expressed as follows:
- the C/N ratio of the frequency spectrum analyzer is almost equal to the C/N ratio of the first local oscillator 31. Since the first local oscillator 31 is a wide range sweep oscillator, typically a YIG tuned voltage controlled oscillator, which is expensive and is difficult to further decrease its phase noise.
- the frequency of the first local oscillator is divided by the ratio of N before being mixed with the input signal to be analyzed. Accordingly, the overall carrier wave to noise (C/N) ratio of the spectrum analyzer is improved by the factor of division ratio N.
- the frequency spectrum analyzer for analyzing frequency spectrum of an input signal is comprised of: a first frequency converter formed of a first frequency mixer, a first IF (intermediate frequency) filter and a first local signal oscillator to produce a first IF signal; a second frequency converter which receives the first IF signal and formed of a second frequency mixer, a second IF filter and a second local signal oscillator to produce a second IF signal; a third frequency converter which receives the second IF signal and formed of a third frequency mixer, a third IF filter and a third local signal oscillator to produce a third IF signal which is displayed as frequency spectrum of the input signal; a frequency divider for dividing a frequency of the first local signal by a factor of N; a frequency multiplier for multiplying a frequency of the third local signal; a fourth frequency mixer which is provided with a divided frequency signal from the frequency divider as a fourth local signal; and a fifth frequency mixer which mixes the input signal to be analyzed and
- the local signal supplied to the fifth frequency mixer is produced by a phase lock loop rather than the frequency multiplier of the first embodiment.
- the second embodiment can be achieved with lesser cost than the first embodiment since it does not need the frequency multiplier and the associated band pass filter.
- FIG. 1 is a block diagram showing an example of structure of the frequency spectrum analyzer according to the present invention.
- FIG. 2 is a block diagram showing another example of structure of the frequency spectrum analyzer according to the present invention.
- FIG. 3 is a block diagram showing an example of structure of the frequency spectrum analyzer in the conventional technology.
- the frequency spectrum analyzer of the present invention includes six frequency converters.
- the first to third frequency converters are the same as that of the conventional example of FIG. 3.
- the first frequency converter is formed of a first frequency mixer 11, a first IF (intermediate frequency) filter 21 and a first local oscillator 31 and produces a first IF signal.
- the second frequency converter is formed of a second frequency mixer 12, a second IF filter 22 and a second local oscillator 32 and produces a second IF signal.
- the third frequency converter is formed of a third frequency mixer 13, a third IF filter 23 and a third local oscillator 33 and produces a third IF signal.
- the fourth frequency converter is formed of a frequency mixer 14 and a frequency divider 40 which divides the frequency of the first local oscillator 31 by N.
- the fifth frequency converter is formed of a frequency mixer 15, a frequency multiplier 45 which multiplies the frequency of the third local oscillator 33 by n, a band pass filter 24 and a low pass filter 25.
- the sixth frequency converter is formed of a frequency mixer 16, the third local oscillator 33, a programmable frequency divider 41 which divides the frequency of the third local oscillator 33 by a specified rate, and a band pass filter 26.
- the example of FIG. 1 further includes switches SW1, SW2 and SW3.
- the frequency spectrum analyzer of FIG. 1 has the same configuration as that of FIG. 3.
- the frequency spectrum analyzer further includes a ramp wave generator 50, a detector 60 and a display 70.
- An input signal F1 to be analyzed is converted its frequency by the frequency mixer 15 which mixes the input signal F1 and a fifth local signal F5 from the frequency multiplier 45 through the band pass filter 24.
- the fifth local signal to the mixer 15 has a frequency which is n times higher than the frequency of the third local signal oscillator 33.
- the frequency mixer 15 produces a fourth IF signal which is provided to the frequency mixer 14 through the low pass filter 25.
- the frequency mixer 14 mixes the fourth IF signal and a fourth local signal from the frequency divider 40.
- the fourth local signal to the frequency mixer 14 has a frequency which is 1/N of the first local signal oscillator 31.
- the frequency mixer 14 provides a fifth IF signal having the same frequency as that of the second IF signal to the second IF filter 22.
- the fifth IF signal is mixed with the third local signal by the third frequency mixer 13 and converted to the third IF signal.
- the third IF signal is detected its amplitude by the detector 60 and supplied to the display 70 where it is displayed as frequency spectrum.
- the equation (7) means that the phase noise of the spectrum analyzer is reduced by 1/N, i.e, the C/N ratio of the spectrum analyzer is increased by N times.
- the first local oscillator 31 is a wide range sweep oscillator typically using a YIG (yttrium-iron-garnet) resonator having a C/N ratio of 100 dBc/Hz at 10 kHz offset.
- the second local oscillator 32 is a fixed frequency oscillator such as a dielectric resonance oscillator having a C/N ratio of 110 dBc/Hz at 10 kHz offset
- the third local oscillator 33 is a fixed frequency crystal oscillator having a C/N ratio of 145 dBc/Hz at 10 kHz offset.
- the overall C/N ratio in the conventional example of FIG. 3 is 100 dBc/Hz or less, since the phase noise of the first local oscillator controls the overall phase noise.
- the overall phase noise becomes significantly lower than that of the first local oscillator 31.
- the overall C/N ratio becomes 124 dBc/Hz, which is better than the conventional frequency spectrum analyzer by 24 dB.
- the switch 3 is set to the terminal b to shift the frequency of the fifth local signal to the frequency mixer 15.
- the frequency of the third local oscillator 33 is divided by the programmable divider 41 into 1/5 or 1/6 of the original frequency.
- the output of the programmable divider 41 is mixed with the original third local signal in the frequency mixer 16 to produce, for example, (1+1/5) of the third local signal frequency.
- the shifted frequency local signal is supplied to the frequency multiplier 45 through the filter 26 and is multiplied by n to produce the fifth local signal F5' whose frequency is different from that of the input signal F1. Accordingly, the frequency mixer 15 produces an IF signal to be provided to the frequency mixer 14.
- the input frequency range to be analyzed is reduced because of the decrease in the sweep frequency range of the local signal applied to the frequency mixer 14.
- the switches 1 and 2 are set to the terminals N to achieve the operation of the conventional frequency spectrum analyzer.
- the second embodiment of the present invention will be described with reference to FIG. 2.
- the local signal supplied to the frequency mixer 15 is produced by a circuit configuration different from that of the first embodiment.
- the second embodiment employs a phase lock loop (PLL) 80 rather than the multiplier 45 in the first embodiment.
- PLL phase lock loop
- the example of FIG. 2 further includes frequency dividers 46 and 47.
- the PLL 80 is formed of a phase comparator 81, a programmable divider 84, a loop filter 82 and a voltage controlled oscillator 83.
- the voltage controlled oscillator 83 is, for example, a dielectric resonance oscillator whose oscillation frequency is controlled by a control voltage from the loop filter 82.
- the oscillation frequency is divided by the programmable divider 84 having a dividing ration of 1/5, for example, and is given to the phase comparator 81.
- the phase comparator 81 compares the phases of the signal from the programmable divider 84 and the third local signal F3 and generates a difference signal representing the phase difference between the two.
- the loop filter 82 defines the closed loop characteristics by filtering the difference signal to provide the control signal to the voltage controlled oscillator 83.
- the voltage controlled oscillator 83 By the negative feedback loop of the PLL, the voltage controlled oscillator 83 generates a local signal which has a frequency five times higher than the third local signal F3 while its phase is locked to the phase of the third local signal F3.
- the output frequency of the voltage controlled oscillator 83 is divided by the frequency divider 46 and is supplied to the frequency mixer 15 as the fifth local signal F5.
- the switch 3 Similar to the first embodiment, to avoid the situation where the input signal F1 and the fifth local F5 have the same frequency, the switch 3 is provided to set to the terminal b to shift the frequency in such a situation.
- the overall carrier wave to noise (C/N) ratio is improved by the factor of dividing ratio N as in the same manner described with reference to FIG. 1. It is considered that the example of FIG. 2 can be achieved with less cost than the example of FIG. 1 since it does not need the frequency multiplier and the associated band pass filter.
- the frequency spectrum analyzer is capable of significantly reducing the overall phase noise by dividing the frequency of the first local oscillator.
- the frequency spectrum analyzer of the present invention can improve the carrier to noise (C/N) ratio by using an additional circuit of relatively simple and low cost.
- the frequency spectrum analyzer of the present invention is capable of analyzing frequency spectrum of input signal with a wide dynamic range and high resolution. Moreover, the frequency spectrum analyzer of the present invention can switch between the high C/N ratio mode with a relatively small frequency range and the conventional frequency spectrum analyzer mode.
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- Physics & Mathematics (AREA)
- Mathematical Physics (AREA)
- General Physics & Mathematics (AREA)
- Superheterodyne Receivers (AREA)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP9-287106 | 1997-10-20 | ||
JP28710697A JP3340654B2 (ja) | 1997-10-20 | 1997-10-20 | スペクトラムアナライザ |
Publications (1)
Publication Number | Publication Date |
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US6166533A true US6166533A (en) | 2000-12-26 |
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Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US09/170,301 Expired - Fee Related US6166533A (en) | 1997-10-20 | 1998-10-13 | Frequency spectrum analyzer with high C/N ratio |
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US (1) | US6166533A (de) |
JP (1) | JP3340654B2 (de) |
DE (1) | DE19848293C2 (de) |
Cited By (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6275020B1 (en) * | 1998-05-14 | 2001-08-14 | Advantest Corporation | Frequency analysis method and sweep type spectrum analyzer |
WO2002029426A1 (fr) * | 2000-10-02 | 2002-04-11 | Advantest Corporation | Procede de mesure a balayage a conversion de frequence |
US6621277B2 (en) * | 2001-10-30 | 2003-09-16 | Agilent Technologies, Inc. | Phase noise measurement module and method for a spectrum analyzer |
US20060025946A1 (en) * | 2004-07-28 | 2006-02-02 | Jenkins Keith A | Integrated spectrum analyzer circuits and methods for providing on-chip diagnostics |
US20060064260A1 (en) * | 2004-09-20 | 2006-03-23 | Stein Anatoli B | Spectrum Analyzer with phase noise compensation |
US20070297524A1 (en) * | 2006-06-13 | 2007-12-27 | Ben Jones | Approach for spectrum analysis in a receiver |
US20090140732A1 (en) * | 2007-12-04 | 2009-06-04 | Headway Technologies, Inc. | Low cost simplified spectrum analyzer for magnetic head/media tester |
US20090160430A1 (en) * | 2007-12-20 | 2009-06-25 | Anritsu Company | HAND-HELD MICROWAVE SPECTRUM ANALYZER WITH OPERATION RANGE FROM 9 KHz TO OVER 20 GHz |
WO2014015238A1 (en) * | 2012-07-20 | 2014-01-23 | Resmed Sensor Technologies Limited | Range gated radio frequency physiology sensor |
USD786841S1 (en) * | 2016-05-04 | 2017-05-16 | Kenu, Inc. | Apparatus for mounting a portable electronic device in a vehicle |
US9959883B2 (en) * | 2015-10-06 | 2018-05-01 | The Trustees Of Princeton University | Method and system for producing low-noise acoustical impulse responses at high sampling rate |
US10312862B2 (en) * | 2014-12-30 | 2019-06-04 | Solid, Inc. | Up-down converter |
Families Citing this family (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE102004037577A1 (de) * | 2004-08-03 | 2006-03-16 | Rohde & Schwarz Gmbh & Co. Kg | Verfahren zum Messen des Phasenrauschens eines Hochfrequenzsignals und Meßgerät zum Ausführen dieses Verfahrens |
EP1657558B1 (de) * | 2004-11-10 | 2008-07-23 | Advantest Corporation | Beseitigung der Spiegelfrequenz in Frequenzumsetzern für Spektralanalysatoren |
JP5007834B2 (ja) * | 2008-09-22 | 2012-08-22 | 富士電機株式会社 | オーバーライト特性の測定におけるイメージ妨害信号を回避する制御方法、および、その制御装置 |
CN102095930B (zh) * | 2010-12-22 | 2013-03-06 | 中国电子科技集团公司第十二研究所 | 无预选器频谱仪外混频方式下的外部自动信号识别方法 |
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US4672308A (en) * | 1985-12-05 | 1987-06-09 | Rohde & Schwarz - Polarad, Inc. | Enhanced frequency determination for spectrum analyzers or the like |
US4710702A (en) * | 1985-04-13 | 1987-12-01 | Anritsu Corporation | Heterodyne type signal-measuring method and a measuring apparatus including automatic detuning correction means |
US5168213A (en) * | 1990-03-13 | 1992-12-01 | Hewlett-Packard Company | Swept signal analysis instrument and method |
US5736845A (en) * | 1994-11-11 | 1998-04-07 | Advantest Corp. | Spectrum analyzer having image frequency eliminating device |
US5818215A (en) * | 1995-04-21 | 1998-10-06 | Advantest Corporation | Direct digital synthesizer driven phase lock loop spectrum analyzer |
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US4799020A (en) * | 1987-02-06 | 1989-01-17 | Tektronix, Inc. | Time variant frequency correction technique |
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1997
- 1997-10-20 JP JP28710697A patent/JP3340654B2/ja not_active Expired - Fee Related
-
1998
- 1998-10-13 US US09/170,301 patent/US6166533A/en not_active Expired - Fee Related
- 1998-10-20 DE DE19848293A patent/DE19848293C2/de not_active Expired - Fee Related
Patent Citations (5)
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US4710702A (en) * | 1985-04-13 | 1987-12-01 | Anritsu Corporation | Heterodyne type signal-measuring method and a measuring apparatus including automatic detuning correction means |
US4672308A (en) * | 1985-12-05 | 1987-06-09 | Rohde & Schwarz - Polarad, Inc. | Enhanced frequency determination for spectrum analyzers or the like |
US5168213A (en) * | 1990-03-13 | 1992-12-01 | Hewlett-Packard Company | Swept signal analysis instrument and method |
US5736845A (en) * | 1994-11-11 | 1998-04-07 | Advantest Corp. | Spectrum analyzer having image frequency eliminating device |
US5818215A (en) * | 1995-04-21 | 1998-10-06 | Advantest Corporation | Direct digital synthesizer driven phase lock loop spectrum analyzer |
Cited By (25)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6275020B1 (en) * | 1998-05-14 | 2001-08-14 | Advantest Corporation | Frequency analysis method and sweep type spectrum analyzer |
WO2002029426A1 (fr) * | 2000-10-02 | 2002-04-11 | Advantest Corporation | Procede de mesure a balayage a conversion de frequence |
US20040041554A1 (en) * | 2000-10-02 | 2004-03-04 | Kouji Miyauchi | Frequency conversion sweep measuring method |
US6861833B2 (en) | 2000-10-02 | 2005-03-01 | Advantest Corporation | Frequency conversion sweep measuring method |
US6621277B2 (en) * | 2001-10-30 | 2003-09-16 | Agilent Technologies, Inc. | Phase noise measurement module and method for a spectrum analyzer |
US20070013360A1 (en) * | 2004-07-28 | 2007-01-18 | Jenkins Keith A | Integrated spectrum analyzer circuits and methods for providing on-chip diagnostics |
US7116092B2 (en) | 2004-07-28 | 2006-10-03 | International Business Machines Corporation | Integrated spectrum analyzer circuits and methods for providing on-chip diagnostics |
US7446523B2 (en) | 2004-07-28 | 2008-11-04 | International Business Machines Corporation | Integrated spectrum analyzer circuits and methods for providing on-chip diagnostics |
US20060025946A1 (en) * | 2004-07-28 | 2006-02-02 | Jenkins Keith A | Integrated spectrum analyzer circuits and methods for providing on-chip diagnostics |
US20060064260A1 (en) * | 2004-09-20 | 2006-03-23 | Stein Anatoli B | Spectrum Analyzer with phase noise compensation |
US7124043B2 (en) * | 2004-09-20 | 2006-10-17 | Guzik Technical Enterprises | Spectrum analyzer with phase noise compensation |
US8023575B2 (en) * | 2006-06-13 | 2011-09-20 | Bandspeed, Inc. | Approach for spectrum analysis in a receiver |
US20070297524A1 (en) * | 2006-06-13 | 2007-12-27 | Ben Jones | Approach for spectrum analysis in a receiver |
US20090140732A1 (en) * | 2007-12-04 | 2009-06-04 | Headway Technologies, Inc. | Low cost simplified spectrum analyzer for magnetic head/media tester |
US8525509B2 (en) | 2007-12-04 | 2013-09-03 | Headway Technologies, Inc. | Low cost simplified spectrum analyzer for magnetic head/media tester |
US20090160430A1 (en) * | 2007-12-20 | 2009-06-25 | Anritsu Company | HAND-HELD MICROWAVE SPECTRUM ANALYZER WITH OPERATION RANGE FROM 9 KHz TO OVER 20 GHz |
US8159208B2 (en) * | 2007-12-20 | 2012-04-17 | Anritsu Company | Hand-held microwave spectrum analyzer with operation range from 9 KHz to over 20 GHz |
US9103856B2 (en) | 2007-12-20 | 2015-08-11 | Anritsu Company | Hand-held microwave spectrum analyzer with operation range from 9 KHz to over 20 GHz |
WO2014015238A1 (en) * | 2012-07-20 | 2014-01-23 | Resmed Sensor Technologies Limited | Range gated radio frequency physiology sensor |
US9445729B2 (en) | 2012-07-20 | 2016-09-20 | Resmed Sensor Technologies Limited | Range gated radio frequency physiology sensor |
US10143386B2 (en) | 2012-07-20 | 2018-12-04 | Resmed Sensor Technologies Limited | Range gated radio frequency physiology sensor |
US10863906B2 (en) | 2012-07-20 | 2020-12-15 | Resmed Sensor Technologies Limited | Range gated radio frequency physiology sensor |
US10312862B2 (en) * | 2014-12-30 | 2019-06-04 | Solid, Inc. | Up-down converter |
US9959883B2 (en) * | 2015-10-06 | 2018-05-01 | The Trustees Of Princeton University | Method and system for producing low-noise acoustical impulse responses at high sampling rate |
USD786841S1 (en) * | 2016-05-04 | 2017-05-16 | Kenu, Inc. | Apparatus for mounting a portable electronic device in a vehicle |
Also Published As
Publication number | Publication date |
---|---|
JPH11118847A (ja) | 1999-04-30 |
DE19848293C2 (de) | 2002-05-02 |
JP3340654B2 (ja) | 2002-11-05 |
DE19848293A1 (de) | 1999-04-22 |
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